I'm on the campaign Odessas must be ours and the mission is Never Again. The last thing I have to do is neuralize the air threat (2 planes flying around), but the flak guns next to the water won't reach the planes. How do you take them out?

I might be experiencing some glitches then because I did that and the men follow the planes in the flak gun but do not shoot, and the planes just fly by. Do they have to be taken out with the flak guns?

In the set up, assign a key to the Pitch Down so that you can lift the camera to see the air above.
Face the enemy plane coming direction.
High light the flake gun.
Aim at the enemy plane and press the mouse button to shoot.
Repeat when the enemy plane comes back.
It will be shot down.

In the option, assign a key for Pitch Down.
Use Pitch Down to view the sky.
Face the direction where enemy planes are coming from.
Aim and shoot at the planes using a flak gun.
Repeat shooting when the planes come back again.